Drug-conjugates, conjugation methods, and uses thereof

1. An active agent-conjugate, comprising Formula 1a:

or a pharmaceutically acceptable salt thereof,

wherein:

A is a targeting moiety selected from the group consisting of an antibody and an antibody fragment;

B is null;

X is N;

Y is N;

m is 1;

D is a drug;

L 2 is a linker independently selected from the group consisting of —(CH 2 ) n —, —(CH 2 CH 2 O) n , D-Val-Leu-Lys, Gly-Gly-Arg, and combinations thereof;

n is 1;

L is —NH—C(═O)—NH; and

L 1A is a linker selected from the group consisting of —(CH 2 ) n —, —(CH 2 CH 2 O) n , D Val-Leu-Lys, and Gly-Gly-Arg, or is null.

2. The active agent-conjugate of claim 1 wherein A is a monoclonal antibody (mAB).